Fibers having improved color fastness and fibrous formed body constituted thereof

ABSTRACT

A subject of the invention is to provide a fiber and a fibrous formed body, particularly, a nonwoven fabric all having an exceptional color fastness and high liquid absorption properties and high durable hydrophilic properties. This is attained by a fiber essentially based on at least one kind of thermoplastic resin, wherein a fiber treating agent containing component (A) to (D) described below is attached to the fiber, with specific ratio of each of component (A) to (D), wherein (A) is an alkyl phosphate metal salt in which the number of carbons of an alkyl group is less than 10; (B) is a trialkylglycine derivative; (C) is a hydroxycarboxylic acid; and (D) is an alkyl phosphate metal salt in which the number of carbons of alkyl group is in the range of 10 to 14.

TECHNICAL FIELD

The present invention relates to fibers having an excellent color fastness and excellent liquid absorption properties. Moreover, the invention relates to a fibrous formed body, for example, a nonwoven fabric, using the fibers having the excellent color fastness and the excellent liquid absorption properties.

BACKGROUND ART

Heat-fusible fibers formable by heat fusion are widely used for hygienic goods such as a diaper, a napkin and an absorbent pad, daily necessities, an industrial material such as a filter, and so forth because a nonwoven fabric having a good feeling can be easily obtained with a high safety by utilizing heat energy from hot air, heat rolls or the like. In particular, in the case where the fibers are used for the hygienic goods, high liquid absorption properties are required from necessity of quickly and repeatedly absorbing a liquid such as urine and menstrual blood.

On the other hand, an antioxidant such as dibutylhydroxytoluene is added and contained in the heat-fusible fibers obtained according to relevant methods for the purpose of preventing deterioration by generation of radicals. Therefore, discoloration is easily caused if the fibers are stored in sunshine, directly under a fluorescent lamp, or the like for a long period of time, and thus a problem of deteriorating a quality level of a product frequently arises.

Consequently, a proposal has been made for improving color fastness by adding hydroxycarboxylic acid to a fiber treating agent to be attached onto a fiber surface (Patent literature No. 1, for example). Moreover, a proposal has been made for the purpose of preventing a yellowing phenomenon generated during manufacturing or storing fibers by using an alkyl ammonium phosphate for a fiber treating agent (Patent literature No. 2, for example).

On the other hand, a proposal has been made for improving repeated water permeability of a nonwoven fabric or the like by using a fiber treating agent containing a predetermined component (Patent literatures No. 3 and No. 4, for example).

CITATION LIST Patent Literature

Patent literature No. 1: JP 4381579 B.

Patent literature No. 2: JP 2001-140168 A.

Patent literature No. 3: JP 2002-161477 A.

Patent literature No. 4: JP 2003-239172 A.

SUMMARY OF INVENTION Technical Problem

Although a proposal has been made for improving color fastness of fibers according to the background art, hydroxycarboxylic acid has a low function of giving hydrophilic properties, and therefore may adversely affect liquid absorption properties of the fibers. Moreover, alkyl ammonium phosphate has a low function of giving durable hydrophilic properties, and therefore has a problem of difficulty in obtaining highly durable hydrophilic properties.

Herein, “liquid absorption properties” means a capability of quickly transferring a liquid to an absorption layer in the case where the liquid such as urine and menstrual blood is brought in contact (dripped or the like) from a side of a nonwoven fabric under a state where a fibrous formed body such as the nonwoven fabric is arranged on the absorption layer such as a pulp sheet . The liquid absorption properties are also referred to as liquid permeability, fluid permeability or the like. Moreover, “durable hydrophilic properties” means repeated liquid absorption properties herein.

In view of such a problem, a subject of the invention is to provide fibers and a fibrous formed body, particularly, a nonwoven fabric all having an exceptional color fastness, and high liquid absorption properties and high durable hydrophilic properties.

Solution to Problem

The inventors of the invention have diligently continued research, as a result , have found that the subject can be attained by attaching to fibers a fiber treating agent containing a predetermined amount of each of an alkyl phosphate metal salt, a trialkylglycine derivative and hydroxycarboxylic acid.

Accordingly, the invention includes the constitutions described below.

Item 1. A fiber essentially based on at least one kind of thermoplastic resin, wherein a fiber treating agent containing component (A), component (B), component (C) and component (D) described below is attached to the fibers, a component ratio of each of component (A), component (B) and component (C) is in the range of 3% by mass or more to less than 10% by mass and a component ratio of component (D) is in the range of 40 to 60% by mass, based on an effective component in the fiber treating agent, and the component ratio (% by mass) of component (A) and the component ratio (% by mass) of component (C) satisfy a relationship: component (C)≦component (A); component (A): an alkyl phosphate metal salt in which the number of carbons of an alkyl group is less than 10; component (B): a trialkylglycine derivative; component (C): hydroxycarboxylic acid; and component (D): an alkyl phosphate metal salt in which the number of carbons of an alkyl group is in the range of 10 to 14. Item 2. The fiber according to the item 1, wherein the fiber treating agent further contains component (E) described below in the range of 10 to 20% by mass and component (F) described below in the range of 15 to 25% by mass, in terms of the component ratio based on the effective component in the fiber treating agent; component (E): polyoxyalkylene-modified silicone; and component (F): an ester of an alkyleneoxide adduct of hydroxystearic acid glyceride with maleic acid, wherein the ester is a compound in which a hydroxyl group of the ester is blocked by monocarboxylic acid having 10 to 22 carbons. Item 3. A fibrous formed body, constituted essentially of the fiber according to the item 1 or 2. Item 4. The fibrous formed body according to the item 3, wherein the fibrous formed body is a nonwoven fabric.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the invention, fibers having excellent liquid absorption properties and excellent durable hydrophilic properties, and having an excellent color fastness are obtained by attaching to fibers a fiber treating agent containing a predetermined amount of each of an alkyl phosphate metal salt, a trialkylglycine derivative and hydroxycarboxylic acid. Moreover, a fibrous formed body, for example, a nonwoven fabric can be attained as constituted of such fibers and having excellent liquid absorption properties and excellent durable hydrophilic properties, and having an excellent color fastness.

The invention allows a preferred compatibility of liquid absorption properties, durable hydrophilic properties and color fastness in the fibers and the fibrous formed body.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the invention will be explained in more detail.

Component (A) constituting a fiber treating agent to be attached to fibers according to the invention is an alkyl phosphate metal salt in which the number of carbons of an alkyl group is less than 10. The number of carbons of the alkyl group is preferably in the range of 4 to 8, further preferably, in the range of 6 to 8. Specific examples of the metal salt include an alkali metal salt. Specific examples of the alkali metal salt include a sodium salt, a potassium salt and a lithium salt, preferably, a potassium salt among the salts.

Component (B) constituting the fiber treating agent to be attached to the fibers according to the invention is a trialkylglycine derivative, and a compound having an inner salt between a carboxyl group and quaternary ammonium in which three alkyl groups are bonded with a nitrogen atom in a glycine molecular structure, or the compound having a so-called betaine structure. As for the number of carbons of the alkyl group, component (B) is composed of alkyl groups arbitrarily selected from alkyl groups having 1 to 22 carbons. Compound (B) has particularly preferably two alkyl groups being a lower alkyl group having up to 4 carbons such as methyl and ethyl, and one alkyl group being a long-chain alkyl group having 12 or more carbons. Specific examples of the trialkylglycine derivative include dimethyloctadecylglycine hydroxide and heptadecylimidazolium hydroxyethylglycine hydroxide.

Component (C) constituting the fiber treating agent to be attached to the fibers according to the invention is hydroxycarboxylic acid. Specific examples of the hydroxycarboxylic acid include citric acid, lactic acid, tartaric acid, malic acid and glycolic acid, particularly preferably, citric acid.

A component ratio of each of component (A) , component (B) and component (C) all constituting the fiber treating agent to be attached to the fibers according to the invention is in the range of 3% by mass or more to less than 10% by mass in an effective component in the fiber treating agent. More specifically, the component ratios (% by mass) of component (A) and component (C) are required to satisfy a relationship: component (C) 5 component (A). The component ratio (% by mass) of each component of component (A), component (B) and component (C) further preferably satisfies a relationship: component (C) component (B) component (A).

Hydroxycarboxylic acid as component (C) has an effect on improving color fastness. If the component ratio of hydroxycarboxylic acid as component (C) is in the range of 3% by mass or more to less than 10% by mass, the effect on improving the color fastness is sufficient, and simultaneously liquid absorption properties are not extremely decreased. The component ratio of hydroxycarboxylic acid as component (C) is preferably in the range of 3 to 5% by mass.

Because the liquid absorption properties due to the fiber treating agent tend to be decreased by adding hydroxycarboxylic acid as component (C) to the fiber treating agent as a constituent, the alkyl phosphate metal salt in which the number of carbons of the alkyl group is less than 10 as component (A) is needed as a component for compensating for a decrease in the liquid absorption properties. The alkyl phosphate metal salt in which the number of carbons of the alkyl group is less than 10 is the component for maintaining and improving the liquid absorption properties. The component ratio thereof is in the range of 3% by mass or more to less than 10% by mass based on the effective component in the fiber treating agent. Component (A) is in the above range, and thus durable hydrophilic properties are not adversely affected. The component ratio is further preferably in the range of 5% by mass or more to less than 10% by mass.

The relationship of the component ratio of each of the alkyl phosphate metal salt in which the number of carbons of the alkyl group is less than 10 as component (A), and hydroxycarboxylic acid as component (C) both constituting the fiber treating agent is required to satisfy the relationship: component (C) component (A) in the relationship of the composition ratios (% by mass) of component (A) and component (C) because component (A) compensates for a decrease in the liquid absorption properties caused by adding component (C) as described above.

The trialkylhydroxyglycine derivative as component (B) is a component for giving the durable hydrophilic properties, and the component ratio thereof is in the range of 3% by mass or more to less than 10% by mass based on the effective component in the fiber treating agent. The component (B) compensates for a decrease in the durable hydrophilic properties caused by adding the alkyl phosphate metal salt as component (A). Component (B) is in the above component ratio, and thus good durable hydrophilic properties can be given, and the color fastness is not decreased, either. Component (B) has further preferably a composition ratio in the range of 3 to 7% by mass.

In the fiber treating agent to be attached to the fibers according to the invention, the component ratios among the trialkylhydroxyglycine derivative as component (B), the alkyl phosphate metal salt in which the number of carbons of the alkyl group is less than 10 as component (A), and the hydroxycarboxylic acid as component (C) further preferably satisfy the relationship: component (C) component (B) component (A) in the component ratio (% by mass) of each component in view of the color fastness, the liquid absorption properties and the durable hydrophilic properties.

In addition, “effective component” described above means a component excluding water content from the whole of the fiber treating agent.

Component (D) constituting the fiber treating agent to be attached to the fibers according to the invention is the alkyl phosphate metal salt in which the number of carbons of the alkyl group is in the range of 10 to 14. Although component (D) is a component for giving the liquid absorption properties and antistatic properties in a manner similar to component (A), component (D) has a larger number of carbons than component (A) has, and therefore has a role of assisting a component for improving smoothness of a fiber surface and giving the durable hydrophilic properties in addition to giving the liquid absorption properties. The number of carbons of the alkyl group is in the range of 10 to 14, and thus the liquid absorption properties are not significantly decreased. Specific examples of the metal salt include an alkali metal salt. Specific examples of the alkali metal salt include a sodium salt, a potassium salt and a lithium salt, preferably, the potassium salt among the salts.

The component ratio of the alkyl phosphate metal salt as component (D) is in the range of 40 to 60% by mass, further preferably, in the range of 45 to 55% by mass in the effective component in the fiber treating agent.

A specific embodiment of the fibers according to the invention includes fibers containing a fiber treating agent attached to fibers further containing component (E) described below in the range of 10 to 20% by mass and component (F) described below in the range of 15 to 25% by mass, in terms of the component ratio based on the effective component.

Component (E) constituting the fiber treating agent to be attached to the fibers according to the invention is polyoxyalkylene-modified silicone, preferably, represented by the general formula described below.

(wherein R represents methylene, propylene, N-(aminomethyl)methylimino or N-(aminopropyl)propylimino, X represents a polyoxyalkylene group. Then n and m indicate integers, respectively, selected from numbers in such a range that content of Si is in the range of 20 to 70% by mass and molecular weight is in the range of 1,000 to 100,000.)

The content of Si in the modified silicone is in the range of 20 to 70% by mass. Specific examples of the polyoxyalkylene group include a polyoxyethylene group, a polyoxypropylene group, a polyoxybutylene group, and a group in which the above constitutive monomers are copolymerized. The modified silicone contains at least 20% by mass of a polyoxyethylene moiety relative to a polyoxyalkylene moiety. The modified silicone has the molecular weight preferably in the range of 1,000 to 100,000, particularly preferably, in the range of 7,000 to 15,000 in view of giving hydrophilic properties. The component ratio of component (E) in the fiber treating agent is suitably in the range of 10 to 20% by mass. If the component ratio of component (E) is in the range of 10 to 20% by mass, sufficient hydrophilic properties are developed and a quick water permeability is acquired. Furthermore, the amount of wetback is also suppressed, no decrease of durable hydrophilic properties is caused, and no dropping of the treating agent from the fibers by water permeation or the like easily occurs.

Component (F) constituting the fiber treating agent to be attached to the fibers according to the invention is an ester of an alkyleneoxide adduct of hydroxystearic acid glyceride with maleic acid, wherein the ester is a compound in which a hydroxyl group of the ester is blocked with monocarboxylic acid having 10 to 22 carbons. The alkyleneoxide adduct of hydroxystearic acid glyceride is obtained by allowing an addition reaction of alkyleneoxide to an ester composed of hydroxystearic acid and glycerin being a polyhydric alcohol. Component (F) is the ester of the compound with maleic acid, in which the reaction molar ratio thereof is preferably in the range of 1.5:1.0 to 2.0:1.0, and the hydroxyl group of the ester is blocked with monocarboxylic acid having 10 to 22 carbons such as lauric acid and stearic acid.

Molecular weight of component (F) is large to give durability to the treating agent by the action thereof, and can suppress dropping of other highly hydrophilic components from the fiber surface by water permeation or the like. The component ratio of component (F) in the fiber treating agent is suitably in the range of 15 to 25% by mass. If the component ratio of component (F) is in the above range, the durable hydrophilic properties are good, the hydrophilic properties due to the treating agent are maintained and resistance to liquid absorption is not increased.

In the fibers or a fibrous formed body, for example, a nonwoven fabric, according to the invention, the effective component in the fiber treating agent described above is suitably attached to the fibers in the range of 0.1 to 1.0% by mass, preferably, in the range of 0.3 to 0.8% by mass based on the mass of the fibers. If the amount of attachment to the fibers is 0.1% by mass or more, antistatic properties are preferably sufficiently developed, and no static electricity is preferably generated in a process for processing the fibers having the attached fiber treating agent into the fibrous formed body such as the nonwoven fabric, and thus processing preferably tends to be facilitated. If the amount of attachment is 1.0% by mass or less, dropping of the fiber treating agent from the fibers is preferably small, accumulation in equipment is preferably not increased, and thus processability is preferably not deteriorated in the process for processing the fibers.

As an embodiment of attaching the fiber treating agent to the fibers, the fiber treating agent maybe attached to the fibers, and then the fibers may be processed into the fibrous formed body as required. Alternatively, the fibers are processed into the fibrous formed body, and then the fiber treating agent may be attached to the fibrous formed body.

The fibrous formed body, for example, the nonwoven fabric, according to the invention can be processed and manufactured according to a suitable process using the fibers to which the above fiber treating agent is attached, or can be manufactured by attaching the above fiber treating agent to the fibrous formed body obtained by being processed from the fibers according to a suitable process. For example, in the case where the fiber treating agent is attached to the fibrous formed body such as the nonwoven fabric, the fiber treating agent may be clearly attached uniformly to the whole body, may be attached to an arbitrary part as required, or may be attached in a different amount for each part to be attached.

Specifically, the fiber treating agent can be attached to the fibers or the fibrous formed body such as the nonwoven fabric in a state of emulsion in which the fiber treating agent is diluted with ion exchange water or the like in a concentration in the range of 3 to 30% by mass. The fiber treating agent may be attached to the fibers in a process for producing the fibers, namely, a so-called spinning process, drawing process or crimp process, or the fiber treating agent may be attached to the nonwoven fabric to be in a desired range in the amount of attachment after the fibers are processed into the fibrous formed body, for example, after the fibers are processed into the nonwoven fabric. As a method for attaching the fiber treating agent to the fibers, publicly known methods such as an oiling roll method, a dipping method and a spraying method can be applied. Specific examples of a method for attaching the fiber treating agent to the nonwoven fabric include an oiling roll method (coating method), a dipping method and a spraying method. For improving efficiency and fixing properties of attachment, corona discharge treatment or normal-pressure plasma discharge treatment may be applied to the nonwoven fabric as pretreatment.

Adjustment of the amount of the fiber treating agent attached to the fibers or the fibrous formed body can be carried out with the number of roll rotations or the like in the case where the fiber treating agent is attached with a roll such as an oiling roll, or with a spraying amount or the like in the case where the fiber treating agent is attached by the spraying method.

Specific examples of methods for quantitatively confirming the amount of the fiber treating agent attached to the fibers include an extraction method using a solvent . The amount of the attached fiber treating agent per unit mass can be confirmed by dipping a predetermined amount of the fibers or the fibrous formed body into a solvent, for example, methanol, ethanol or 2-propanol, in which the fiber treating agent intended for confirming the amount of attachment is soluble, evaporating only the solvent with heat or the like and measuring the remaining amount. Specific examples include a rapid method and a Soxhlet method.

Other publicly known surfactant components can be used for the fiber treating agent to be attached to the fibers according to the invention within the range in which advantageous effects of the invention are not adversely affected. Specific examples of the surfactant components include an antistatic agent such as sodium alkanesulfonate, and a nonionic component such as sorbitan acid ester.

A variety of additives can be mixed with the fiber treating agent to be attached to the fibers according to the invention within the range in which advantageous effects of the invention are not adversely affected. Specific examples of the additives include an emulsifier, a preservative, an anti-rust agent, a pH regulator and an antifoaming agent.

The fibers according to the invention may be single-component fibers or conjugate fibers. A thermoplastic resin constituting the fibers is not particularly limited. Specific examples include a polyolefin resin such as high density polyethylene, linear low density polyethylene, low density polyethylene, polypropylene (propylene homopolymer), an ethylene-propylene copolymer composed mainly of propylene, an ethylene-propylene-l-butene copolymer composed mainly of propylene, polybutene-1, polyhexene-1, polyoctene-1, poly-4-methylpentene-1, polymethylpentene, 1,2-polybutadiene and 1,4-polybutadiene, and a polyester resin such as polyethylene terephthalate, polypropylene terephthalate, polybutyrene terephthalate, polylactic acid, polybutylene succinate, polybutylene adipate terephthalate and a copolymerized polyester (copolyester). The fibers may be constituted of a mixture containing two or more kinds thereof.

Specific examples of the conjugate fibers include conjugate fibers having a concentric sheath-core structure, an eccentric sheath-core structure and a side-by-side structure as a cross-sectional structure, and split conjugate fibers having an alternating radial shape. Specific examples of a shape of the fibers include a round, star, elliptic, triangular, quadrangular, pentagonal, multifoil or hollow shape. Specific examples of combinations of resins for the conjugate fibers (combinations as a sheath/core or a low-melting point component/high-melting point component) includes high density polyethylene/polypropylene, low density polyethylene/polypropylene, an ethylene-octene copolymer/polypropylene, an ethylene-propylene copolymer/polypropylene, an ethylene-propylene-butene-1 copolymer/polypropylene, high density polyethylene/polyethylene terephthalate, an ethylene-octene copolymer/polyethylene terephthalate, an ethylene-propylene-butene-1 copolymer/polyethylene terephthalate, polypropylene/polyethylene terephthalate, high density polyethylene/polybutyrene terephthalate and polylactic acid/polybutylene succinate. A ratio of the sheath/core or the low-melting point component/high-melting point component is preferably in the range of 10/90 to 90/10 in a mass ratio, particularly preferably, in the range of 30/70 to 70/30 in view of spinnability, drawing properties and nonwoven fabric processability.

To the thermoplastic resin constituting the fibers according to the invention, an additive such as an antioxidant, a light stabilizer, an ultraviolet light absorber, a neutralizer and a nucleating agent may be further added appropriately as required within the range in which advantageous effects of the invention are not adversely affected.

An antibacterial agent, a flame retardant, a smoothing agent, an antistatic agent, a pigment, and inorganic particulates for giving flexibility may be added to the fibers according to the invention appropriately as required within the range in which advantageous effects of the invention are not adversely affected. Specific examples of methods for addition include a method for directly adding powder thereof or a method for preparing a masterbatch from the powder and kneading the masterbatch. As a resin used for preparing the masterbatch, a resin identical to the thermoplastic resin constituting the fibers is most preferably used, but the resin is not particularly limited thereto, and a different resin may also be used if the resin meets requirements of the invention.

The fibers according to the invention can be suitably obtained by a melt spinning method or a spunbond method each using the resin containing the thermoplastic resin described above, for example. In the case of short fibers, the fibers can be obtained by obtaining undrawn fibers according to the melt spinning method, promoting partial orientation and crystallization in a drawing process, giving crimp in a crimp process, applying heat treatment for a fixed period of time at a predetermined temperature using a hot-air dryer or the like, and then cutting the obtained product into an arbitrary length.

A denier of the fibers according to the invention is not particularly limited, but preferably is in the range of 0.3 to 12.0 dtex. The denier is, further preferably, in the range of 1.0 to 8.0 dtex, still further preferably, in the range of 1.2 to 6.0 dtex in view of a process for processing the fibers into the nonwoven fabric.

Length of the fibers according to the invention is not particularly limited, and can be determined arbitrarily for each method for processing the fibers into the nonwoven fabric. For example, in the case of short fibers with which a fiber web is formed using a roller carding machine, the length of the fibers is preferably in the range of 25 to 125 millimeters, further preferably, in the range of 38 to 76 millimeters. In the case where an air-laid machine is used, the length of the fibers is preferably in the range of 3 to 25 millimeters, further preferably, in the range of 3 to 12 millimeters.

A method for processing the fibers into the nonwoven fabric is not particularly limited. A technique is preferably used in which the fiber web is formed, and then heat treatment is performed to thermally bond entangled points of the fibers constituting the fiber web, and to process the fibers into the nonwoven fabric. Specific examples of the method for forming the fiber web include a carding method for allowing the fibers to pass through the roller carding machine, an air-laid method for forming the fiber web by means of air and a spunbond method for laminating long fibers. As a method for heat-treating the fiber web and thermally bonding the entangled points of the fibers, publicly known machines can be used, such as a hot-air circulation dryer, a hopper-type heat-treatment machine, a relaxing hot-air dryer, a Yankee dryer, a drum dryer, an infra-red dryer and a partial thermocompression bonding processing machine.

Unit weight (mass per unit area) of the nonwoven fabric in the case of processing the fibers according to the invention into the nonwoven fabric is not particularly limited, and can be determined according to an intended application. For example, the unit weight of a surface material of a disposable diaper and a sanitary napkin is preferably in the range of 10 to 50 g/m², further preferably, in the range of 20 to 35 g/m².

The fibrous formed body according to the invention comprises, in addition to the nonwoven fabric as described above, a fibrous tow, a fiber web, a fibrous laminate, a net, a knitted or woven fabric, and a material processed into a sheet or mass by heat-treating the above bodies, and a material prepared by superimposing nonwoven fabrics in a layer or waveform and applying secondary processing such as heat treatment. Specific examples of the fibrous formed body according to the invention include the nonwoven fabric, in particular.

Specific examples of textile products using the fibers or the fibrous formed body, for example, the nonwoven fabric, according to the invention include an absorbent article such as a diaper, a napkin and an incontinence pad, a medical and sanitary material such as a gown and a surgical gown, an indoor interior material such as a wall sheet, shoji paper and a floor material, life-related material such as a cover cloth, a cleaning wiper and a kitchen garbage cover, a toiletry product such as a disposable toilet and a toilet cover, a pet product such as a pet sheet, a pet diaper and a pet towel, an industrial material such as a wiping material, a filter, a cushioning material, an oil adsorbent and an ink tank adsorbent, a general medical material, a bedding material and a nursing care product. The fibers or the fibrous formed body according to the invention can be applied to various textile products.

EXAMPLES

Hereinafter, the invention will be explained in detail by way of Examples, but the invention is in no way limited by the Examples. In addition, manufacture, processing, measurement and testing in each example were carried out by the methods shown below.

Examples 1 to 9 and Comparative Examples 1 to 5 (Thermoplastic Resin)

A resin described below was used as a thermoplastic resin constituting fibers.

Resin 1 : high density polyethylene having a density of 0.96 g/cm³, an MFR (190° C., load: 21.18 N) of 16 g/10 min. and a melting point of 130° C. (abbreviation: PE-1). Resin 2 : high density polyethylene having a density of 0.96 g/cm³, an MFR (190° C., load: 21.18 N) of 41 g/10 min. and a melting point of 130° C. (abbreviation: PE-2). Resin 3: polypropylene having an MFR (230° C., load: 21.18 N) of 16 g/10 min. and a melting point of 162° C. (abbreviation: PP-1). Resin 4: polypropylene having an MFR (230° C., load: 21.18 N) of 28 g/10 min. and a melting point of 162° C. (abbreviation: PP-2). Resin 5: polypropylene having an MFR (230° C., load: 21.18 N) of 11 g/10 min. and a melting point of 162° C. (abbreviation: PP-3). Resin 6: ethylene-propylene-butene-1 copolymer having an ethylene content of 4.0% by weight and a 1-butene content of 2.65% by weight, an MFR (230° C., load: 21.18 N) of 16 g/10 min. and a melting point of 131° C. (abbreviation: co-PP).

(Measurement of Melt Mass-Flow Rate (MFR))

A melt mass-flow rate was measured in accordance with JIS K7210. Herein, MI was measured in accordance with condition D (testing temperature : 190° C., load: 2.16 kg) , and MFR was measured in accordance with condition M (testing temperature: 230° C., load: 2.16 kg), in Table 1 of Appendix A.

(Manufacture of Fibers)

As shown in Table 1 and Table 2 described below, a spinnerette allowing a concentric sheath-core cross section was used, and an extrusion output was adjusted to be 50/50 in a volume ratio in a fiber cross section at an extrusion temperature to perform melt-spinning of a thermoplastic resin, and thus undrawn fibers were obtained. On the occasion, a fiber treating agent shown in Table 1 and Table 2 was emulsified and attached to fibers using an oiling roll. After drawing the thus obtained undrawn fibers by means of a heat roll at 90° C. to 2.2 dtex fibers and giving crimp, the fibers were dried by means of a hot-air circulation dryer and cut into a length of 51 millimeters by means of a cutter, and thus short fibers were obtained.

As shown in columns of “Form during fiber treating agent attachment” in Table 1 and Table 2, Examples 1 to 7 and Comparative Examples 1 to 4 were carried out by attaching the fiber treating agent to the fibers, and Examples 8 and 9 and Comparative Example 5 were carried out by attaching the fiber treating agent to a nonwoven fabric as described later.

(Composition of Fiber Treating Agent)

Compositions of fiber treating agents used in each example were shown in Table 1 and Table 2. Units of the compositions were expressed in terms of % by mass, and the total amount of effective components in the fiber treating agents should be 100% by mass.

The components of the fiber treating agents in Table 1 to Table 2 were expressed using abbreviations as shown below.

-   -   A: potassium octyl phosphate.     -   B: dimethyloctadecylglycine hydroxide.     -   C: citric acid.     -   D1: potassium lauryl phosphate.     -   D2: potassium tridecyl phosphate.     -   E: polyoxyethylene-modified silicone.     -   F: ester of a maleic acid ester of polyoxyethylene (20 mol)         caster wax (2:1 in a molar ratio) and stearic acid (2:1 in a         molar ratio).

(Nonwoven Fabric Processing)

In Examples 1 to 7 and Comparative Examples 1 to 4, short fibers obtained in the above process were processed into a fiber web by means of a roller carding test machine (made by Daiwa-kiko corporation Ltd.), and the web was subjected to thermal bonding by through-air processing (abbreviated as TA in Tables 1 and 2) at a temperature described in Table 1 and Table 2 by using a suction dryer. Thus, a nonwoven fabric having a unit weight of about 23 plus minus 2 g/m² was obtained.

Examples 8 and 9 and Comparative Example 5

In Example 8, short fibers obtained without attaching a fiber treating agent in manufacturing the fibers were processed into a fiber web by means of a roller carding test machine (made by Daiwa-Kiko corporation Ltd.), and the web was subjected to thermal bonding by through-air processing (abbreviated as TA) at a temperature described in Table 2 by using a suction dryer. Thus, a nonwoven fabric having a unit weight of about 23 plus minus 2 g/m² was obtained.

In Example 9 and Comparative Example 5, a spunbond nonwoven fabric was obtained according to a spunbond method using a resin described in Table 2. Specifically, a spinnerette allowing a concentric sheath-core cross section was used, and an extrusion output was adjusted to be 50/50 in a volume ratio in a fiber cross section at an extrusion temperature described in Table 2. A group of composite long fibers output from the spinnerette was introduced into an air sucker, sucked and drawn, and processed into fibers having a fiber diameter of 2.2 dtex. Then, the group of the long fibers discharged from the air sucker was charged by giving electric charges with charging apparatus, opened by collision with a reflector, and a group of opened long fibers was collected, as a long fiber web, on an endless net conveyer provided with a suction device on a rear face. The collected long fiber web was subjected to partial thermocompression bonding processing (abbreviated as PB in Table 2) with an embossing roll (projection) having a compression bonding area ratio of 21%/flat roll at a linear pressure of 80 N/mm. Thus, a nonwoven fabric having a unit weight of about 23 plus minus 2 g/m² was obtained.

After the above nonwoven fabrics were dipped into an emulsion of the fiber treating agent shown in Table 2, the nonwoven fabrics were dehydrated and dried so as to contain a predetermined amount of attachment.

(Measurement of Amount of Treating Agent Attachment)

In the case of short fibers to which a fiber treating agent was attached within a process for manufacturing the fibers, measurement was carried out using 2 g of material processed into a fiber web by means of a roller carding test machine by using a fast residual-oil extractor (“R-II model” made by Tokai Keiki K. K.). In the case where a fiber treating agent was attached to a nonwoven fabric after fibers were processed into the nonwoven fabric, measurement was carried out using 2 g of the nonwoven fabric. Then 25 milliliters of methanol were used as an extraction solvent.

The amount of attachment was calculated by the following equation:

Amount of treating agent attachment (% by mass)=extraction (g) 2×100.

(Testing of Color Fastness)

In the case of short fibers to which the fiber treating agent was attached within the process for manufacturing the fibers, the fibers were processed into a carded web by means of a roller carding test machine, and the web was processed into a nonwoven fabric having a unit weight of 200 plus minus 20 g/m² by a needle-punch processing method. The nonwoven fabric was cut into a 8 cm long and 8 cm wide piece, and the cut piece was used as a test sample.

In the case where the fiber treating agent was attached to the nonwoven fabric after the fibers were processed into the nonwoven fabric, the nonwoven fabric was cut into 80 mm long and 80 mm wide pieces, and the pieces were superimposed to be 200 plus minus 20 g/m² in the total unit weight, and the superimposed pieces were used as a test sample. The test sample was placed at 80 centimeters above an oil stove fire source (ambient temperature: 100±5° C.), and exposed to combustion gas for 3 hours. Then the sample was removed. Numerical values of Yellow Index (YI) of on a surface of the test sample before and after testing were measured by means of a color-difference meter (“Model SM-4” made by Suga Test Instruments Co. , Ltd.) , and ΔYI as a difference thereof was calculated.

In addition, test results were rated as described below. If a numerical value of ΔYI was 6 or less, color fastness was exceptional and therefore rated as ‘A’ . If the numerical value is in the range of 7 to 8, the color fastness was rated as ‘B’ , but if the numerical value is 9 or more, color change may be judged high, and thus the color fastness was rated as ‘C’.

(Absorption Test)

A liquid absorption test in accordance with NONWOVENS/LIQUID STRIKE-THROUGH TIME of EDANA RECOMMEND TEST METHODS was conducted. The test was repeated three times and durable hydrophilic properties were tested. As test equipment,

“Lister” made by Lenzing Instruments GmbH & Co KG was used. As a test sample, a 100 mm long and 100 mm wide piece cut out from a material processed into a nonwoven fabric was used. As a filter paper (water absorption paper), “Kimtowel Wiper White (made by Nippon Paper Crecia Co., Ltd.)” was used.

In addition, results of liquid absorption tests were rated by classifying the results into three levels according to a period of time required for liquid absorption as described below.

Material Processed into a Nonwoven Fabric by Through-Air Processing of Short Fibers

If the period of time was 0.5 second or less, the liquid absorption properties were judged exceptional and rated as ‘A’.

If the period of time was over 0.5 second and less than 1.0 second, the liquid absorption properties were rated as ‘B’.

If the period of time was 1.0 second or more, the liquid absorption properties were judged poor and rated as ‘C’.

Material Processed into a Nonwoven Fabric by Partial Thermocompression Bonding Processing According to a Spunbond Method

If the period of time was 1.5 seconds or less, the liquid absorption properties were judged exceptional and rated as ‘A’.

If the period of time was over 1.5 seconds and less than 2.0 seconds, the liquid absorption properties were rated as ‘B’.

If the period of time was 2.0 seconds or more, the liquid absorption properties were judged poor and rated as ‘C’.

Results of a third absorption test were considered as an indicator of durable hydrophilic properties, and rated by classifying the results into three levels according to a period of time required for liquid absorption as described below.

Material Processed into the Nonwoven Fabric by Through-Air Processing of Short Fibers

If the period of time was 1.5 seconds or less, the durable hydrophilic properties were judged exceptional and rated as ‘A’.

If the period of time was over 1.5 seconds and less than 2.0 seconds, the durable hydrophilic properties were rated as ‘B’.

If the period of time was 2.0 seconds or more, the durable hydrophilic properties were judged poor and rated as ‘C’.

Material Processed into the Nonwoven Fabric by Partial Thermocompression Bonding Processing According to the Spunbond Method

If the period of time was 3.0 seconds or less, the durable hydrophilic properties were judged exceptional and rated as ‘A’.

If the period of time was over 3.0 seconds and less than 4.0 seconds, the durable hydrophilic properties were rated as ‘B’.

If the period of time was 4.0 seconds or more, the durable hydrophilic properties were judged poor and rated as ‘C’.

For each Example and Comparative Example, conditions for obtaining fibers and a nonwoven fabric using the fibers, and results of testing and measuring performance of the fibers and the nonwoven fabric according to the testing and measuring methods described above are shown in the following Table 1 and Table 2, collectively.

TABLE 1 Example Example Example Example Example Example Example 1 2 3 4 5 6 7 Thermoplastic resin Core PP-1 PP-3 PP-3 PP-3 PP-3 PP-3 PP-3 (abbreviation/ ingredient (260) (270) (270) (270) (270) (270) (270) extrusion Sheath PE-1 co-PP co-PP co-PP co-PP co-PP co-PP temperature (° C.) ingredient (240) (250) (250) (250) (250) (250) (250) Volume ratio (core/sheath) 50/50 50/50 50/50 50/50 50/50 50/50 50/50 Fibrous form Short Short Short Short Short Short Short fibers fibers fibers fibers fibers fibers fibers Nonwoven fabric processing 130(TA) 138(TA) 138(TA) 138(TA) 138(TA) 138(TA) 138(TA) temperature (TA or TB) Unit weight (g/m²) 25 25 25 24 24 24 24 Specific volume (cm³/g) 60 50 50 50 50 50 50 Form during fiber treating agent Fibers Fibers Fibers Fibers Fibers Fibers Fibers attachment Amount of fiber treating agent    0.45    0.45    0.45    0.50    0.50    0.50    0.50 attachment (%) Component A  7  7  9  3  9  9  7 ratio of fiber B  5  5  9  3  9  7  5 treating agent C  3  3  9  3  7  3  3 (% by mass) D1 40 40 35 45 30 35 45 D2 10 10  5  5 10  5 15 E 15 15 15 20 20 16 10 F 20 20 18 21 15 25 15 Potassium — — — — — — — stearyl phosphate Absorption Liquid A A A B B A A performance absorption properties Durable A A B A B A B hydrophilic properties Color fastness (ΔYI) A A A B A B B

TABLE 2 Compar- Compar- Compar- Compar- Compar- ative ative ative ative ative Example Example Example Example Example Example Example 8 9 1 2 3 4 5 Thermoplastic resin Core PP-1 PP-2 PP-1 PP-3 PP-3 PP-3 PP-2 (abbreviation/ ingredient (260) (260) (260) (270) (270) (270) (260) extrusion Sheath PE-1 PE-2 PE-1 co-PP co-PP co-PP PE-2 temperature (° C.) ingredient (240) (240) (240) (250) (250) (250) (240) Volume ratio (core/sheath) 50/50 50/50 50/50 50/50 50/50 50/50 50/50 Fibrous form Short Short Short Short Short Short Short fibers fibers fibers fibers fibers fibers fibers Nonwoven fabric processing 130(TA) 127(PB) 130(TA) 138(TA) 138(TA) 138(TA) 127(PB) temperature (TA or PB) Unit weight (g/m²) 25 24 23 25 23 24 24 Specific volume (cm³/g) 60 15 60 50 50 50 15 Form during fiber Non- Non- Fibers Fibers Fibers Fibers Non- treating agent attachment (%) woven woven woven fabric fabric fabric Amount of fiber treating agent    0.45    0.40    0.46    0.46    0.41    0.52    0.40 attachment Component A  9  9 — — —  7  3 ratio of fiber B  7  5 15 14  5 —  5 treating agent C  3  3 —  5  3  3  9 (% by mass) D1 36 38 40 39 40 40 48 D2 10 10 — — 10 10 10 E 15 15 15 14 18 20 10 F 20 20 20 19 24 20 15 Potassium — — 10 9 — — — stearyl phosphate Absorption Liquid A A B C C B C performance absorption properties Durable A A A B A C C hydrophilic properties Color fastness (ΔYI) A A C B C B A

INDUSTRIAL APPLICABILITY

Fibers according to the invention have both an excellent color fastness, and excellent liquid absorption properties and excellent durable hydrophilic properties as obtained by attaching a fiber treating agent containing a predetermined amount of an alkyl phosphate metal salt, a trialkylglycine derivative and hydroxycarboxylic acid. In carrying out the invention, better fibers can be provided by further attaching, as an effective component in a fiber treating agent, polyoxyalkylene-modified silicone, and an ester of an alkyleneoxide adduct of hydroxystearic acid glyceride with maleic acid, wherein the ester is a compound in which a hydroxyl group of the ester is blocked with monocarboxylic acid.

Furthermore, a fibrous formed body such as a nonwoven fabric constituted of the fibers according to the invention has high liquid absorption properties and high durable hydrophilic properties, and exceptional color fastness. Thus, the fibrous formed body can be advantageously used for applications of various textile products including an absorbent article such as a diaper, a napkin and an incontinence pad, a medical and sanitary material such as a gown and a surgical gown, an indoor interior material such as a wall sheet, shoji paper and a floor material, a life-related material such as cover cloth, a cleaning wiper and a kitchen garbage cover, a toiletry product such as a disposable toilet and a toilet cover, a pet product such as a pet sheet, a pet diaper and a pet towel, an industrial material such as a wiping material, a filter, a cushioning material, an oil adsorbent and an ink tank adsorbent, a general medical material, a bedding material and a nursing care product. 

1. A fiber essentially based on at least one kind of thermoplastic resin, wherein a fiber treating agent containing component (A), component (B), component (C) and component (D) described below is attached to the fiber, a component ratio of each of component (A), component (B) and component (C) is in the range of 3% by mass or more to less than 10% by mass and a component ratio of component (D) is in the range of 40 to 60% by mass, based on an effective component in the fiber treating agent, and the component ratio (% by mass) of component (A) and the component ratio (% by mass) of component (C) satisfy a relationship: component (C)≦component (A); component (A): an alkyl phosphate metal salt in which the number of carbons of an alkyl group is less than 10; component (B): a trialkylglycine derivative; component (C): a hydroxycarboxylic acid; and component (D): an alkyl phosphate metal salt in which the number of carbons of an alkyl group is in the range of 10 to
 14. 2. The fiber according to claim 1, wherein the fiber treating agent further contains component (E) described below in the range of 10 to 20% by mass and component (F) described below in the range of 15 to 25% by mass, in terms of the component ratio based on the effective component in the fiber treating agent; component (E): a polyoxyalkylene-modified silicone; and component (F): an ester of an alkyleneoxide adduct of hydroxystearic acid glyceride with maleic acid, wherein the ester is a compound in which a hydroxyl group of the ester is blocked with monocarboxylic acid having 10 to 22 carbons.
 3. A fibrous formed body, constituted essentially of the fiber according to claim
 1. 4. The fibrous formed body according to claim 3, wherein the fibrous formed body is a nonwoven fabric.
 5. A fibrous formed body, constituted essentially of the fiber according to claim
 2. 6. The fibrous formed body according to claim 5, wherein the fibrous formed body is a nonwoven fabric. 